From the autoextremist:

Anyone heard anything about this?

 

why would I want a big V8 tht only puts out ~200HP when I could have a V6 that does 240-300 or a larger displacement V8 that gets 300-500HP?

 

how is the new Z06 an example of small block development reaching its limit?

 

 

I'll bet my Z28 that NASCAR will NEVER, EVER, NOT IN 10,000 YEARS switch to a displacement under 300 cubic inches. Or ever adopt a Formula 1 style V8. These guys are still running carbs and a suspension setup similar to that from the 1960's.

 

That is one of the dumbest articles I've read. Who is this moron?

 

I once read an article about how to remove ones head from ones ****.

It was exilerating, I think I'll email that guy a copy.

 

It's tough to imagine that one could substantially increase the intake port cross-section beyond that of the LS7, so that engine probably does represent something close to the useful limit of the GenIII/IV design.

My friends and I, when kicking around ways for GM to distinguish their product, came up with the idea of baby V8 engines. Given a fixed displacement (such as, oh, 2.4 L), more cylinders = potentially more horsepower, but at the cost of a peakier powerband that's higher in the rev range (yea, I know, counterintuitive to everything we "know" about I4s versus V8s, but that's the way it is). It's possible that this could work with some of the new 6- and 7-speed transmissions that are coming out, but it's hard to imagine such an engine being practical for mainstream usage.

 

I was actually thinking, the past week or so, that GM could develop a OHV 'mini' block for its FWD and smaller RWD cars. Imagine a Solstice with a 4.5 L version of the LS2. Literally 3/4 of the current LS2. Shrink Every dimension. 300 hp and it could be used in a 3 series size Malibu and Colorado. Keep the traditional small block for trucks, vettes, and large cars. You could sh*t can the OHC engines in Caddies and Buicks because people would get a smoother operation thanks to the smaller displacement and get the great sound of a V8. Also they would have the cylinder count over their competition. Then GM could be almost all OHV 2.4 Ecotec, HV 60°, Miniblock, Small block, N*.

But 2.4 L is WAY to small.

 

Cool, that's something I'm Interested in.

 

Who though the sun was setting on the great American v8???? It's the dawn of a new age to me. The number of new v8 cars on the road has to be more this year then for any year in a long time.

 

I've posted about engine dynamics a few times in other threads, but this one bears the duty of repeating it one more time...

With internal combustion engines, there is a VERY pronounced law of diminishing returns which correlates the number of pistons, the size of the bore, the stroke, and the friction related to all of the above.

Quick (and really oversimplified) example...
(It is critical that both engines in this example have the same stroke, as that ensures that their linear piston speed - the speed the piston and rings are sliding in the cylinder - are the same.)
Let's say I have a 350ci engine that is a single cylinder. If the stroke is 4.0", then the cylinder would have to be 87.5sq-in, or a diameter of 10.55" . The ring circumference will be 33.16", so we will have 33.16 inches of ring rubbing the cylinder walls (i.e. friction).

Now if I have a 350ci engine with 8 cylinders and a stroke of 4", then each hole will contribute 43.75ci, will be 10.94sq-in in area, and the dia will be 3.73". The ring circumference is then 11.72"... PER CYLINDER.
So if I multiply the ring length times 8 cylinders, we see 93.789 linear inches of compression ring that will be rubbing the cylinder walls for the V8, as compared to the 33.16 linear inches of compression ring rubbing the cylinder walls on the single-cylinder engine. That's a ratio of almost 3:1 MORE FRICTION generated by the rings in the V8 over the single cylinder engine, given the same piston speed (aka RPM). The same principles apply to the journal bearings, rod bearings, wrist pins, cam bearings, cam/tappet interface, tappet bores, rocker arm pivots, etc, etc. That's A LOT more friction to overcome in the V8!

One thing that counteracts this increased friction is the benefit of getting better burn rates in certain volumes and shapes of combustion chambers. The flamefront can only propagate so fast, and it needs time to burn completely to be efficient, otherwise we see flames coming out the tailpipe as unburned fuel exits the engine - wasteful no doubt. Using fundamental physics, there is then a ratio of cylinder volume/rpm that allows optimal fuel burning (if geometry is fixed - no exotic heads/domed pistons and such). So a smaller cylinder (like our 3.73" cylinder above) will burn more efficiently and rev to higher RPM than our gigantic 10.55" cylinder. In fact it will burn significantly better - enough so that it offsets the friction losses and still provides more mechanical (useable) power than the single cylinder unit.
Another benefit is smoother operation and reduced vibration. The single cylinder gives a big hit once every 720 degrees, whereas the V8 gives a smaller hit every 90 degrees of crank rotation. This gives a much smoother application of torque to the driveline.

When taking my first Automotive Powerplants course in college, we studied some really bizzare alternatives, and had the opportunity to see all kinds of approaches to get around the friction issue - everything from the Wankel Cycle to the Diesel. Again, it simply turns out that for running @5000 RPM, the optimal engine is a V8 with between 5.0 and 5.7 liters displacement. For a V6 the optimum is between 3.5 and 4.0 liters. There were oodles of charts and graphs that showed how increasing bore or stroke had adverse effects on efficiency and/or power. For example, you can trade a little power for better torque by lengthening the stroke and decreasing bore (to keep the same displacement). You will gain torque thru the added offset in the crank, but you will lose HP because the rings will be travelling faster against the cylinder walls to cover the added stroke distance thereby making more friction.

My point in all of this is that I am skeptical that a tiny V8 will prove worthwhile in the long run. I can see them making screamers that will bust 10,000RPM no problem, and they will probably find the HP figures, but the torque will be hard to find with tiny cranks that have little offsets for rod journals. And then there's the efficiency issue.
Tiny V8's can be done for sure, but is it worth it?
In my opinion - NO. It's a world of trade-offs.
I'd rather have a V6 or even a good I6 or I5 before I'd wrestle with a tiny V8. Look at it this way, even if all else is equal, the V6 has fewer moving parts, which means less risk of breakage and/or potential problems... the KISS principle rises again.

And that's my .02 on tiny V8's.

 

Good Post; Very Informative. Thanks.

Which brings me back to GM's Rotary Engine. Should they investigate this technology or are they too far behind Forgien manufacturers??

 

Wankels just arent as efficient right now (though getting better), and most people arent used to the feel of the motors and how to work with them. Emissions is very hard to meet as well, and life expectancy isnt as good as the apex seals do wear. The seals are getting much better from the 12a and 13b, but they're not perfect. Because of those i dont think it'll be as likely.

One company (cant find the link at the moment) made a 2.6L Hayabusa based v8. Generated a LOT of good power. Downside is lifetime. Motorcycle engines (and any engine given to lots of high revving) wont last long. Fuel efficiency is great, but replacing half the truck engines in the fleet because they failed under warranty isnt.

Also the LS7 is physically at its limit, but technology isnt over yet. Valvetrain has improved, but there is more that can be done there. Solenoid operated valves for example... Yes it'd be hard to increase the port cross section, but going to 4 valve heads would change things.

The v8 is on its way out when more cars have v8's then anything I've seen in my lifetime?? Uh-huh. Sure. The v8 is on its way out when Dodge offers numerous v8's (and only v8's) in the Charger? When GM makes a new v8 thats 7L because the 6L just didnt make enough power???

That sums it up perfectly.

 

Ok if the stroke is the same then there is no better result using less displacement. But what if the bore/stroke ratio is the same but the physical size is less, including external dimensions?

Does the law of diminishing returns exist the same or is it different?